1. Field of the Invention
The present invention relates to a piezoelectric vibrator unit suitable for an ink jet recording head and an ink jet recording head using the piezoelectric vibrator unit. In particular, the present invention relates to a piezoelectric vibrator unit having curved portions which correspond to deformable regions of the vibrator unit.
2. Description of the Related Art
An actuator unit in which minute regions (arrayed at fixed pitches) are deflected is disclosed in Japanese Patent Laid-Open Publication No. Sho. 58-7364. The actuator unit includes a lower electrode, formed on the surface of a thin plate, which is elastically deformable. A green sheet, which is shaped like a rectangular strip and made of piezoelectric material, is layered on the thin plate surface with the lower electrode by bonding or coating. The resultant structure is sintered to form a piezoelectric layer. In addition, upper electrodes are formed on the surface of the sintered structure.
However, the bonding or coating process, by which the rectangular green sheet made of piezoelectric material is layered on the thin plate's surface is an essential step in the manufacture of the above-mentioned actuator unit. Therefore, the manufacturing of the actuator unit is inefficient. Furthermore, the lower electrode is easily peeled away from the piezoelectric layer in the sintering process. In this respect, the actuator unit is poor in durability.
To cope with this, a unique actuator unit is proposed in Japanese Patent Laid-Open Publication No. Sho. 62-101455. The actuator unit includes a thin elastic plate made of ceramic which has an electromechanical displacing property. A ceramic piece is inserted in a region of the elastic plate which is to be deflected. In addition, electrodes are attached to both sides of the region containing the ceramic piece.
The actuator unit described above eliminates the need for the bonding or coating process associated with the green sheet of piezoelectric material. In addition, the piezoelectric member has a single layer structure. Therefore, it rarely happens that the electrode is peeled away. However, the actuator unit has the following disadvantage. An elasticity and a rigidity of a vibrating region of the elastic plate are substantially equal to those in a non-vibrating region. Therefore, a displacement of the vibrated region by its deflection is small. Accordingly, when the actuator unit is applied to an ink jet recording head in which the volume of the pressure generating chamber is varied in order to discharge an ink droplet, a high voltage is required in order to drive the recording head.